Terbium

Atomic Number:

65

Atomic Radius:

221 pm (Van der Waals)

Atomic Symbol:

Tb

Melting Point:

1356 °C

Atomic Weight:

158.9

Boiling Point:

3230 °C

Electron Configuration:

[Xe]6s24f9

Oxidation States:

3

History

Discovered by Mosander in 1843. Terbium is a member of the lanthanide or "rare earth" group of elements. It is found in cerite, gadolinite, and other minerals along with other rare earths. It is recovered commercially from monazite in which it is present to the extent of 0.03%, from xenotime, and from euxenite, a complex oxide containing 1% or more of terbia.

Production

Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. As with other rare earth metals, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible.

Properties

Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289°C. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color.

Uses

Sodium terbium borate is used in solid-state devices. It can be used with ZrO2 as a crystal stabilizer of fuel cells which operate at elevated temperature. Few other uses have been found.

Handling

Little is known of the toxicity of terbium. It should be handled with care as with other lanthanide element